Carpet tiles are typically composed of a fibrous or wear-type surface and an undersurface secured to a primary backing and containing a thick layer of a thermoplastic backing material, such as for example, of polyvinyl chloride resin as a solid or a foam, bitumen or atactic polypropylene. Often glass fiber scrim or tissue is employed with the primary backing and embedded in the backing layer in order to impart dimensional stability to the carpet tile. Typical carpet tiles and carpet tile production methods are described for example in U.S. Pat. No. 4,582,554 issued Apr. 15, 1986 hereby incorporated by reference.
It is desirable to provide for a carpet tile which has a low flame resistance and low smoke value. Flame-resistant carpets have been prepared by applying a carboxylated cross-linkable vinyl chloride resin composition to the back surface of a thermoplastic backing sheet which serves as the primary backing and then heating the vinyl chloride composition to cross-link the vinyl chloride resin and to bond the tufted yarns to the base of the primary backing. In such a method, the temperature of the cross-linking in heating is maintained below the shrinkable temperature of the polymeric fibrous primary backing is then laminated to the surface of the cross-linked vinyl chloride resin composition (see for example U.S. Pat. No. 3,661,691 issued May 9, 1972 hereby incorporated by reference).
The flame-retardant, vinyl-foam carpet and method of the patent provides for improved flame resistance by bonding the surface of the primary backing coated with a cross-linked vinyl resin to a secondary backing wherein the primary and secondary backing are prevented from shrinking and separating when exposed to open-flame conditions. This improvement is related to flame-retardant vinyl-foam backing carpet and not to carpet tile, which requires a very thick, heavy thermoplastic backing layer to secure a free-lay, dimensionally stable carpet tile.